1. Field of the Invention
The invention relates to measuring the susceptibility of a magnetic transducer head to wear. More specifically, the invention relates to a method and device for simulating thermal effects at the interface of a magnetic head and a magnetic recording medium.
2. Background of Related Art
The interface between a magnetic head and a recording medium is a major concern in a recording system. Ideally, the head should make intimate contact with the recording medium to minimize spacing loss. The head and the medium, on the other hand, should move relative to each other free and easy to minimize wear and tear on both.
Aside from its magnetic characteristics, wear rate and dimensional stability are two of the most important factors of a magnetic head. Of these, wear is a prime consideration. To extend its useful life, the design of a magnetic head and its surface material, where it contacts a recording medium, have been the object of much study.
As a part of that study, it is desirable to determine the ability of the magnetic head (record and playback) to withstand wear at its interface with the recording medium, before magnetic recording/playback apparatus is marketed commercially. Knowing the wear-resistant capability of a magnet head is particularly important for high-density magnetic recording apparatus because even the smallest of wear-induced abnormalities at the head-to-medium interface can contribute to degradation of high-resolution (short wavelength) information.
A commonly employed procedure for determining wear-resistant capability of a magnetic head is to transport a magnetic storage medium (either tape or disk) in operative contact with the head for an extended period of time, e.g. several hours or more. For example, U.S. Pat. No. 4,091,654 discloses a device and method for testing the abrasive quality of a magnetic recording head. The recording head is a "dummy" made of polished steel or other material, the smoothness of which has been determined prior to the head actually contacting a magnetic recording surface. After a given amount of contact between the dummy head and a magnetic tape, a fiber optic emitter/detector measures the smoothness of the head by means of converting light reflected from the surface of the head into a corresponding voltage output.
A problem with a procedure of this type is that it provides no information concerning the rate at which the transducer head is wearing during the tape transport interval. Furthermore, the test fails to identify specific sub-microscopic regions of the head where wear actually occurs.
U.S. Pat. No. 3,753,093 discloses a device for determining the degree of abrasiveness of a magnetic tape. To that end, the tape passes over a simulated recording head which is made from an electrically nonconducting material and which geometrically approximates the dimensions of an actual recording head at its interface with the tape. The working surface of the simulated recording head, i.e. the surface that actually contacts the tape, has deposited thereon one or more strips of a magnetic alloy similar to the magnetic alloy of an actual recording head. Each strip extends from one simulated pole tip to the other simulated pole tip (across the length of a simulated head gap) in the direction of tape-transport movement. During a tape-transport operation, electrical test equipment monitors the increase in the electrical resistance of the magnetic alloy strip to determine the abrasiveness of the magnetic tape.
Although a procedure of this type is intended to provide information concerning the rate at which a magnetic alloy strip is wearing, it also suffers from a disadvantage in that sub-microscopic areas of the head subject to wear and are not readily identifiable by the measurements made; furthermore, the procedure requires a complex, and therefore expensive, multi-step process for depositing the strips of magnetic alloy and for depositing conducting gold films that are needed to provide electrical contact between each alloy strip and the electrical test equipment.